Since it seems people are interested;
Iron Lung Notes!
1: His wrists are roughed up from handcuffs
2: Eden and The COI are at odds (the fathers speech at the beginning mentions the COI not sharing their findings and Simon mentions the COI making him burn off his eden tattoo, not in reference to his conviction, Eden obviously doesn't believe there's anything to find to save humanity)
3: He has a length of string around his wrist with a broken loop attached, and the scene where he finds his pendant alludes to it previously being attached to that loop
4: He's rational in most situations and can take a lot before he begins to crumble. He gets angry but most often for good reason. (Though, he's less rational if it means survival, for example the water and the isopropyl. ) Even when in need of some sort of comfort and offered a voice to keep him company, he acknowledges that he's likely concussed or experiencing a more logical phenomenon. Even when reality begins to crumble, he asks questions to parse through what's reality and what's not.
5: He self-soothes often, whether with the knife sheath or the pendant or breathing routines. It makes sense considering he seems to resent his own anger.
6: He's resourceful, likely stemming from a childhood and adulthood having to care for and fend for himself, whether through the rapture or after being imprisoned. Either way, he makes do with whatever he can get.
7: It may be a coincidence, but at full speed, the ships throttle looks like the Eden symbol.
8: He tries both "password" and "password1" on the sm8 blackbox programme, before trying "fuck you" when it doesn't work. When he gets angry, it says "I'm sorry butcher".
9: He ultimately cares a lot, maybe too much given his reality. He apologises even in situations where he's justified, and he apologises to inanimate objects. Either he's deeply remorseful, or offers everything else what he needs.
10: "I see you." "I see you." "Agreed." Three different voices. The first seems to be the eel, the second is Simon, who is the third?
11: The figure Simon sees after the interaction with the light is himself, after his mutations take full effect. The teeth on the side of the face, the missing left arm, and the shape of the nose give it away.
12: His hair is either braided or twisted into the half ponytail he wears it in
13: His mothers voice is a part of the cacophony when he's navigating back to the sm8. Her lines include "they have a tree" "it'll feel just like home" "you'll love it there". As well, another voice (likely Ava) says someone confiscate something and that "they hope to make a garden of their own someday". She likely is referencing the seedlings like Simon carries, which likely implies they're a symbol many or all members of Eden carry.
14: When heading down to get Simon, Ava tells David to ready the 14, meaning there's another and possibly more subs ready and waiting every time one is sent down.
15: The blood gets progressively more corrosive as time goes on, as seen by how his arms slowly become more damaged but one drip almost immediately burns into his forehead. This could help explain how he rips his own arm off to save himself.
16: At the end, the seedling in Simon's pendant grows due to the blood and sprouts into a tree, through the sub and the eel, effectively exploding both. This as well proves the accelerating strength of the blood. (I also believe the blood is the antagonist in the movie, not the eel. The eel is a byproduct of it.)
If you want to, send me asks about any of these and I'll yap lol